Selection of rice varieties suitable for double cropping in Thailand was actively initiated in the sixties. A series of semi-dwarf high-yielding varieties were released from the initial RD varieties with off numbers designating the non-glutinous endosperm types and even numbers the glutinous ones, respectively.
Since 1969, eight non-glutinous varieties and three glutinous varieties have been released so far. Grain quality is among the top priorities for selection.